It is universally recognized that torsional stiffness is one of the most important properties of a vehicle chassis, [
1
]. There are several reasons for which high chassis stiffness is preferable. Lack of chassis torsional stiffness affects the lateral load transfer distribution, it allows displacements of the suspension attachment points that modify suspension kinematics and it can trigger unwanted dynamic effects like resonance phenomena or vibrations, [
2
].
The present paper introduces two analytical vehicle models that constitute an efficient tool for a correct evaluation of the main effects of chassis torsional stiffness on vehicle dynamics. In the first part an enhanced steady-state vehicle model is derived and employed for the analysis of the vehicle handling. The model takes account of chassis torsional stiffness for the evaluation of the lateral load transfer and, by means of the concept of the axle cornering stiffness, includes the effects of tire non-linear behavior.
In the second part of the paper a linear four-degrees-of-freedom model is presented. The frequency response of the vehicle subjected to steering inputs is analyzed. The influence of chassis torsional stiffness on the modes of motion and their dependency on the vehicle parameters is investigated.
Simulations of the behavior of two real vehicles are introduced and a sensitivity analysis is presented.